Old Drug Holds Promise Against Opportunistic Lung Bug

ROCHESTER, N.Y., Aug. 19 /PRNewswire-USNewswire/ -- A drug to
treat inflammation plays a surprising role reducing the level of
infection caused by an opportunistic bug that is deadly for AIDS
and cancer patients and others with weakened immune systems.

The drug, sulfasalazine, spurs the body to get rid of the fungal
evaders by enhancing the body's ability to chew them up instead of
leaving the debris to litter the lungs, where it would continue to
provoke an onslaught of harmful inflammation.

Besides opening a new avenue for research on Pneumocystis
pneumonia or PCP, caused by the fungus Pneumocystis jirovecii, the
work with mice also offers the possibility of manipulating immune
cells called macrophages to improve treatment of infections.

The findings by scientists at the University of Rochester
Medical Center were published August 19 in the journal PLoS
Pathogens.

During a bout with Pneumocystis, the lungs become a battlefield,
where the body pits an array of impressive forces against marauding
microbes. But even when the body gets the upper hand, the damage is
tremendous. Immune cells like neutrophils and macrophages can flood
the lungs, literally suffocating the patient. And when the debris
from dead microbes fills the lungs, more and more immune cells are
called in to clean up the area, making matters worse. It becomes
harder and harder to breathe.

"Many people assume that once the microbe is dead, patients
usually start to feel better immediately. But with Pneumocystis,
patients do not always undergo a rapid clinical improvement
following antibiotic treatment. Even though the bug has been
killed, the debris that is left in the lungs continues to promote
inflammation," said corresponding author Terry Wright, Ph.D., an
infectious disease specialist and associate professor of
Microbiology and Immunology and of Pediatrics.

Pneumocystis is a common bug that infects nearly everyone at
some point; the authors say that more than 80 percent of children
have been infected by the age of 2. Most people shake off the
infection without consequence, but for people with cancer, AIDS, or
other diseases that compromise their immune system, the infection
can be deadly. Usually there are few signs that the patient is sick
until the infection is well established and the fungus is
widespread in the lungs. Among cancer patients, mortality rates as
high as 40 percent have been reported.

Since the body's immune response is central to how Pneumocystis
kills patients, doctors use two different types of drugs in tandem
to treat patients – an antibiotic to kill the bug, and
steroids or another type of drug to reduce the consequent
inflammation.

Central to the study were mice in which the disease progresses
in a manner very similar to AIDS patients. The remarkable strides
in AIDS therapy in recent years have come with a down side for many
patients, thanks to Pneumocystis: When anti-retroviral therapy
kicks in, a patient's immune system often becomes stronger very
quickly – and if the fungus is present, the immune system
attacks it vigorously, causing a potentially deadly form of
pneumonia.

Wright's team looked at the effects in mice of sulfasalazine, an
anti-inflammatory drug that has proven useful in treating
conditions like Crohn's disease and rheumatoid arthritis. The team
found that Pneumocystis-infected mice treated with sulfasalazine
developed much less severe disease than untreated mice. The
sulfasalazine-treated mice had better lung function, less weight
loss, and were generally healthier than untreated animals.

While some of the benefit was due to the drug's
anti-inflammatory properties and was expected, the result included
a big surprise: The drug also spurs the body to remove the bug more
aggressively by boosting the activity of immune cells called
macrophages.

"This was unexpected," said first author Jing Wang, Ph.D.,
research assistant professor in Pediatrics. "Since we reduced the
response of the immune system, you would think the mice would get
sicker. But instead, the mice treated with sulfasalazine were
healthier. At first we thought it was due solely to the
anti-inflammatory activity of the compound, but it turns out that
sulfasalazine actually results in a reduced fungal burden. The drug
helps the body clear the infection.

"We initially thought we had done something wrong, and so we
repeated the experiment again and again. Then, when new technology
was developed, we were able to document that the body cleared the
infection more readily with sulfasalazine," added Wang.

Scientists have long known that the body's immune T cells are
central to the body's response to fight off the infection. The
Rochester team showed that the body's T cells spur macrophages to
attack the fungus – to engulf its particles and chew them up
in a process known as phagocytosis.

While scientists have long suspected that role for macrophages,
the Rochester team relied on a new technology to gather the first
direct evidence of macrophages engulfing fungal particles. The
scientists worked closely with Timothy Bushnell, Ph.D., and others
at Rochester's Flow Cytometry Resources Core, investigating new
ways to use lasers to capture images of molecular events.
Bushnell's team ultimately connected the team with scientists at
Amnis. Together the group developed a new way to capture macrophage
phagocytosis in single cells from mice infected with Pneumocystis.
The technology enabled the team to capture more than 40,000 such
events, compared to just a handful when using conventional
microscopy.

The team showed that as macrophage activity increased, the
animals' health improved and levels of fungus decreased. For
example, 17 days after infection, mice treated with sulfasalazine
had nine times as many macrophages that had engulfed fungal
particles compared to mice that had not been treated with the
compound.

"This marks a new direction in which to look for new therapies
to treat Pneumocystis as well as other inflammatory diseases.
Identifying modulators that can increase or decrease the action of
our immune system in a precise manner is a growing area of
research," said Wright. Recently researchers have come to realize
that there are different kinds of macrophages, and Wright noted
that the type whose activity is trigged by sulfasalazine does not
contribute to inflammation.

In addition to Wang and Wright, other authors include Francis
Gigliotti, M.D., professor of Pediatrics and of Microbiology and
Immunology, and also chief of Infectious Disease at Golisano
Children's Hospital; Samir Bhagwat, Ph.D., research assistant
professor of Pediatrics; and Thaddeus George from the Amnis Corp.
in Seattle. The work was funded by the National Heart Lung and
Blood Institute and the Strong Children's Research Center.

One of the nation's top academic medical centers, the University
of Rochester Medical Center (http://www.urmc.rochester.edu)
forms the centerpiece of the University's health research,
teaching, patient care, and community outreach missions. The
Medical Center receives more than $240 million in external research
funding per year and the University of Rochester School of Medicine
and Dentistry ranks in the top one-quarter of U.S. medical centers
in federal research funding. The University's health care delivery
network is anchored by Strong Memorial Hospital – a 754-bed,
University-owned teaching hospital. As upstate New York's
premier health care delivery network, patients benefit from the
Medical Center's robust teaching and biomedical research
programs.